ORCID Profile
0000-0001-5649-6410
Current Organisations
University of Miami
,
Victoria University
,
University of New South Wales
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Publisher: CSIRO Publishing
Date: 21-02-2023
DOI: 10.1071/WF22009
Abstract: Homogeneous vegetation is widely used in wildland fire behaviour models, although real vegetation is heterogeneous in nature and composed of different kinds of fuels and non-combustible parts. Many features of fires can arise from this heterogeneity. For land management and firefighting, creating heterogeneous fuel areas may be useful to reduce fire intensity and rate of spread (ROS), and alter fire geometry. Recently, an empirical model for fire spread in spinifex grasslands was developed and validated against experimental measurements. In this study, physics-based grassland fire behaviour simulations were conducted with varying percentages of fuel cover and alternating square and rectangular patches of burnable and non-burnable material. The environmental conditions and thermophysical properties of the grassland were kept constant throughout the simulation to separate the effects of fuel heterogeneities from other parameters. For three sets of nominal wind velocities, 3, 5.6 and 10 m s−1, we identified ‘go’ and ‘no go’ fires. Reasonable agreement between the non-dimensionalised simulated ROS and observed ROS in spinifex was found. There is a significant reduction of fire intensity, ROS, flame length, fire width and fire line length due to the heterogeneous effect of vegetation.
Publisher: Elsevier BV
Date: 07-2018
Publisher: Cambridge University Press (CUP)
Date: 08-09-2023
DOI: 10.1017/BAP.2023.22
Publisher: Elsevier BV
Date: 10-2021
Publisher: Informa UK Limited
Date: 02-01-2020
Publisher: Elsevier BV
Date: 2019
DOI: 10.2139/SSRN.3306653
Publisher: Oxford University Press (OUP)
Date: 24-07-2023
DOI: 10.1093/FPA/ORAD020
Abstract: When sender states impose economic sanctions on target states, are the commercially lucrative opportunities for third-party sanctions busters the same across all target states? I develop a time-series cross-sectional data sets using UN Comtrade data between 1963 and 2011 to illustrate how variation in a target state’s economic size impacts the likelihood of sanctions busting. I develop a “Goldilocks” theory of target choice, arguing that target states with medium-sized economies are “just right” with a higher probability of receiving sanctions busting trade than smaller- and larger-sized economies. These “just right” economies likely generate higher rents and more commercially lucrative opportunities than smaller- and larger-sized sanctioned economies. This study has implications for policymakers in that the very policies imposing sanctions tend to target medium-sized economies more frequently. Thus, economic sanctions may stimulate sanctions busting trade and undermine the very behavior these foreign policies are meant to correct.
Publisher: MDPI AG
Date: 25-10-2021
Abstract: The disruptions to wildland fires, such as firebreaks, roads and rivers, can limit the spread of wildfire propagating through surface or crown fire. A large forest can be separated into different zones by carefully constructing firebreaks through modification of vegetation in firebreak regions. However, the wildland fire behaviour can be unpredictable due to the presence of either wind- or buoyancy-driven flow in the fire. In this study, we aim to test the efficacy of an idealised firebreak constructed by unburned vegetation. The physics-based large eddy simulation (LES) simulation is conducted using Wildland–urban interface Fire Dynamic Simulator (WFDS). We have carefully chosen different wind velocities with low to high values, 2.5~12.5 m/s, so the different fire behaviours can be studied. The behaviour of surface fire is studied by Australian grassland vegetation, while the crown fire is represented by placing cone-shaped trees with grass underneath. With varying velocity and vegetation, four values of firebreak widths (Lc), ranging from 5~20 m, is tested for successful break distance needed for the firebreak. For each failure or successful firebreak width, we have assessed the characteristics of fire intensity, mechanism of heat transfer, heat flux, and surface temperature. It was found that with the inclusion of forest trees, the heat release rate (HRR) increased substantially due to greater amount of fuel involved. The non-dimensional Byram’s convective number (NC) was calculated, which justifies simulated heat flux and fire characteristics. For each case, HRR, total heat fluxes, total preheat flux, total preheat radiation and convective heat flux, surface temperature and fire propagation mode are presented in the details. Some threshold heat flux was observed on the far side of the firebreak and further studies are needed to identify them conclusively.
Publisher: Informa UK Limited
Date: 07-02-2020
Publisher: MDPI AG
Date: 08-01-2022
DOI: 10.3390/FIRE5010006
Abstract: Firebrand spotting is a potential threat to people and infrastructure, which is difficult to predict and becomes more significant when the size of a fire and intensity increases. To conduct realistic physics-based modeling with firebrand transport, the firebrand generation data such as numbers, size, and shape of the firebrands are needed. Broadly, the firebrand generation depends on atmospheric conditions, wind velocity and vegetation species. However, there is no experimental study that has considered all these factors although they are available separately in some experimental studies. Moreover, the experimental studies have firebrand collection data, not generation data. In this study, we have conducted a series of physics-based simulations on a trial-and-error basis to reproduce the experimental collection data, which is called an inverse analysis. Once the generation data was determined from the simulation, we applied the interpolation technique to calibrate the effects of wind velocity, relative humidity, and vegetation species. First, we simulated Douglas-fir (Pseudotsuga menziesii) tree-burning and quantified firebrand generation against the tree burning experiment conducted at the National Institute of Standards and Technology (NIST). Then, we applied the same technique to a prescribed forest fire experiment conducted in the Pinelands National Reserve (PNR) of New Jersey, the USA. The simulations were conducted with the experimental data of fuel load, humidity, temperature, and wind velocity to ensure that the field conditions are replicated in the experiments. The firebrand generation rate was found to be 3.22 pcs/MW/s (pcs-number of firebrands pieces) from the single tree burning and 4.18 pcs/MW/s in the forest fire model. This finding was complemented with the effects of wind, vegetation type, and fuel moisture content to quantify the firebrand generation rate.
Publisher: Frontiers Media SA
Date: 28-06-2019
Publisher: CSIRO Publishing
Date: 20-01-2023
DOI: 10.1071/WF21125
Abstract: The interaction of wind and fire on a sloped terrain is always complex owing to the mechanisms of heat transfer and flame dynamics. Heating of unburned vegetation by attached flames may increase the rate of spread. The relative intensities of convective and radiative heat fluxes may change fire behaviour significantly. This paper presents a detailed analysis of flame dynamics, mode of fire propagation and surface radiative and convective heat fluxes on sloped terrain at various wind speeds using physics-based simulations. It was found that with increasing slope angles and wind velocity, the plume inclines more towards the ground and becomes elongated in upslope cases, whereas in downslope cases, the plume rises from the ground earlier. For higher wind velocities, the flame and near-surface flame dynamics appear to show rising, even though the plume is attached. The flame contour results indicate that the near-surface flame dynamics are difficult to characterise using Byram’s number. A power-law correlation was observed between the simulated flame lengths and fireline intensities. The convective heat fluxes are more relevant for wind-driven fire propagation and greater upslopes, whereas both fluxes are equally significant for lower driving wind velocities compared with higher wind velocities.
Publisher: CSIRO Publishing
Date: 20-01-2023
DOI: 10.1071/WF21124
Abstract: This study focuses on physics-based modelling of grassfire behaviour over flat and sloped terrains through a set of field-scale simulations performed using the Wildland–urban Interface Fire Dynamics Simulator (WFDS), with varying wind speeds (12.5, 6 and 3 m s−1) and slope angles (−30° to +30°). To ensure the accuracy of this Large Eddy Simulation (LES), a sensitivity study was carried out to select the converged domain and grid sizes. Fire isochrones, locations of fire front, dynamic and quasi-steady rates of spread (RoS), and fire intensity results from the simulations are presented. Within the simulations conducted, the RoS and fire intensity were found to be higher with increasing slope angles, as well as with wind velocity. RoS comparisons are made with various empirical models. At different slope angles and driving wind velocities, different empirical quasi-steady RoS broadly match with particular dynamic maximum, minimum and averaged RoS values from this study. It appears that the ideal nature of grassfire propagation simulation and challenges related to measuring quasi-steady values in experimental studies are likely reasons for the observed differences. Additionally, for lower wind velocities, the RoS–fire intensity relationship (Byram’s) deviates from linearity for greater upslopes.
Publisher: Elsevier BV
Date: 2020
DOI: 10.2139/SSRN.3684065
Location: United States of America
No related grants have been discovered for Keith Preble.